如何让Hibernate不丢弃表格 [英] How to make Hibernate not drop tables

问题描述

我正在使用hibernate，每当我尝试添加记录时，它都会删除表并重新添加它。它从不使用现有的表并对其进行更改。

这是我的 hibernate.cfg.xml ：



 < hibernate-configuration> 
< session-factory> 
< property name =hibernate.connection.driver_class> org.apache.derby.jdbc.ClientDriver< / property> 
< property name =hibernate.connection.url> jdbc：derby：// localhost：1527 / sample< / property> 
< property name =hibernate.connection.username>用户< / property> 
< property name =hibernate.connection.password>密码< / property> 
< property name =hibernate.connection.pool_size> 10< / property> 
< property name =show_sql> true< / property> 
< property name =dialect> org.hibernate.dialect.DerbyDialect< / property> 
< property name =hibernate.hbm2ddl.auto>更新< / property> 
< property name =current_session_context_class>线程< / property> 
 <！ - 映射实体 - > 
< mapping class =inputDetails.Table1/> 
< mapping class =inputDetails.Table2/> 
 
 
 <！ - 映射资源=contact.hbm.xml/  - > 
< / session-factory> 
< / hibernate-configuration> 
  

这就是我保存数据的方式：



  SessionFactory factory = new Configuration（）。configure（）。buildSessionFactory（）; 
 Session session = factory.getCurrentSession（）; 
 session.beginTransaction（）; 
 // ... 
 session.save（newrecord）
 session.getTransaction（）。commit（）; 
  




解决方案

 <属性名称=hibernate.hbm2ddl.auto>更新< / property> 
  

告诉hibernate在每次创建会话工厂时更新数据库模式。

$ b （）。
$ b

和

  SessionFactory factory = new Configuration（）。configure（）。buildSessionFactory（）; 
  

建立一个新的会话工厂。

在wole应用程序生命周期中，应该只构建一次 SessionFactory 一次。它应该被创建一次然后被重用。您是否阅读过 hibernate参考手册？

I am using hibernate and whenever I try to add a record it drops the table and adds it again. It never uses the existing table and make changes on that.

This is the relevant part of my hibernate.cfg.xml:

<hibernate-configuration>
<session-factory>
  <property name="hibernate.connection.driver_class">org.apache.derby.jdbc.ClientDriver</property>
  <property name="hibernate.connection.url">jdbc:derby://localhost:1527/sample</property>
  <property name="hibernate.connection.username">user</property>
  <property name="hibernate.connection.password">password</property>
  <property name="hibernate.connection.pool_size">10</property>
  <property name="show_sql">true</property>
  <property name="dialect">org.hibernate.dialect.DerbyDialect</property>
  <property name="hibernate.hbm2ddl.auto">update</property>
  <property name = "current_session_context_class">thread</property>
  <!-- Mapping the entities -->
<mapping class="inputDetails.Table1"/>
<mapping class="inputDetails.Table2"/>


  <!--mapping resource="contact.hbm.xml"/-->
</session-factory>
</hibernate-configuration>

This is how I save data:

SessionFactory factory = new Configuration().configure().buildSessionFactory();
    Session session = factory.getCurrentSession();
    session.beginTransaction();
//...
session.save(newrecord)
session.getTransaction().commit();

解决方案

<property name="hibernate.hbm2ddl.auto">update</property>

tells hibernate to update the database schema each time the session factory is created.

And

SessionFactory factory = new Configuration().configure().buildSessionFactory();

builds a new session factory.

A SessionFactory should be built only once during the wole application lifetime. It should be created once and then reused. Have you read the hibernate reference manual?

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